Nebraska used to be abbreviated as NB (at least in Post Office abbreviations). In 1969, it changed to NE for Nebraska. Nevada was abbreviated NEV until 1963 when USPS gave all states 2-letter abbreviations.

I started earning a living in 1960; the youngsters on the bb may not remember the change .

However, I think you are probably right with Nevada for the Fernley plastic piece. The Nevada Casino Promo Token book only lists trinkets from the SS in Reno and Carson City, though. Yours may be a scarce one!